1. Field of the Art
The present invention generally relates to an outboard motor with a bracket assembly, and more particularly relates to an outboard motor that has a bracket assembly to mount a drive unit of the outboard motor on an associated watercraft.
2. Description of Related Art
Typically, outboard motors incorporate a bracket assembly to mount a drive unit thereof on a transom of an associated watercraft. The bracket assembly typically includes a swivel bracket carrying the drive unit for pivotal movement about a steering axis that extends generally vertically, and a clamping bracket supporting the swivel bracket and the drive unit for pivotal movement about a tilt axis extending generally horizontally. The drive unit usually has a propeller in a lower portion thereof to generate propulsion force. Typically, an engine disposed in an upper portion of the drive unit provides power to rotate the propeller through a drive mechanism disposed within the drive unit. For example, Japanese Patent Publication Nos. JP11-310194A and JP2000-289691A disclose such outboard motors.
The lower portion of the drive unit is submerged under water while the propeller propels the associated watercraft. Under the circumstances, a floating object such as, for example, a piece of driftwood can strike the lower portion of the drive unit, or the drive unit can run into a rock under the water while the watercraft travels through in shallow water. A relatively large impact load is exerted on the bracket assembly in those situations. Even though such a load is not exerted, the bracket assembly always receives thrust from the propeller whenever the propeller propels the associated watercraft. The bracket assembly thus is required to endure the various loads or force exerted thereon. More specifically, the swivel bracket and the clamping bracket need to have sufficient rigidity or strength to endure those loads or force.
The thicknesses of the portions of the swivel and clamping brackets which are most subject to such loadings, conventionally are increased to provide the necessary rigidity, and the thickness of the remainder portions thereof are dictated by the thickness of the former portions. In addition, the swivel and clamping brackets are usually produced in a low pressure casting process. Such a method requires the thickness to be relatively large and also requires the entire configuration of the swivel bracket and the clamping bracket to be as simple as possible. Thus, the swivel and clamping brackets are likely to have excessive thickness beyond what is required for rigidity or strength considerations. The entire bracket assembly thus tends to be heavy and cumbersome.